2 Answers

Answer #2 · John Heider's Answer · Hi Donna-Varieties of Iris fall into two major groups, rhizomatous and bulbous. The japanese iris falls under the rhizomatous group. It does not grow from a bulb as most of us are used to seeing in the nurseries. Rhizomes are swollen, horizontally growing underground stems that are used as food storage for the plant.

After removing your plant from its container you will probably see the larger original rhizome. There will probably be other smaller ones growing from this if your plant has been growing in the container for a few seasons. Cut back the leaves to 1/3 their height. Use a sharp knife and separate the rhizomes. The rhizomes should be firm with roots and a group of leaves. Any soft or rotting looking rhizomes should be discarded.

The best time to plant and transplant rhizomatous iris is late July through September. Iris loves the heat and drier weather of summer and the summer dividing will reduce the chance of bacterial soft rot.

When transplanting iris choose a sunny well-drained garden spot. Dig a hole about five inches deep. Build a small mound in the middle of the hole. Place your rhizome on top of the mound and let the roots fall down over the mound. Cover the roots with soil so the rhizome is just slightly exposed. Do not plant the rhizome too deep or it may rot.

The best time to divide Japanese Iris will depend on where you live and garden. Further north, the best time to do so is in early spring. In the South where the climate is warmer, you might be able to achieve good results doing it in early fall. If you divide them in fall, you want to do it early enough so that your new iris will have enough time to establish a good root system before going dormant. Then, in spring, the plants an spend their time establishing upward growth instead of downward root growth.

As with regular irises, division of the Japanese iris is pretty simple. Use a sharp knife to divide the rhizomes from one another. When dividing, cut back three-quarters of the foliage and plant large single or 2 to 4 fans, removing the old rhizomes and roots.

After dividing the rhizomes, plant them 2 to 3 inches deep in new freshly prepared garden beds or soil in containers. Keep the new plants watered regularly for two to three weeks and fertilize them with a flower fertilizer or mild organic plant food every two weeks to help the plants re-establish themselves.

I uploaded a couple pictures of Japanese Iris divisions so that you can know what they look like after having been divided.

Hope this information was helpful. Let us know if you have any further questions. Brent)